Residues of selected antibiotics in water and mud from shrimp ponds in mangrove areas in Viet Nam

Bacterial N-acyl-homoserine lactone enhances the degradation of sulfamethoxazole by microalgae and the associated metabolic regulatory mechanisms

Recent studies have revealed that N-acyl-homoserine lactones (AHLs), common quorum-sensing (QS) signal molecules in Gram-negative bacteria, can also influence microalgal cells. However, their role in regulating the metabolism of pollutants, such as antibiotics, within microalgae remains poorly understood. This study investigated the effects of N-hexanoyl-L-homoserine lactone (C6-HSL) on the degradation of sulfamethoxazole (SMX) in aquaculture wastewater by Chlorella vulgaris. The addition of 0.5 μM C6-HSL resulted in the highest biomass accumulation and the maximum SMX removal efficiency (95.6 %). At optimal concentrations, C6-HSL effectively modulated key secondary messenger signaling pathways including reactive oxygen species (ROS), nitric oxide (NO), and calcium ions (Ca2+) in microalgal cells. Additionally, it upregulated the activity of detoxification enzymes such as glutathione S-transferase (GST) and cytochrome P450 (CYP450), thereby altering SMX degradation pathways and significantly enhancing its removal. Transcriptomic analysis further demonstrated that exogenous C6-HSL upregulated critical genes associated with ROS, Ca2+, and NO signaling, along with genes encoding antioxidant enzymes and those involved in SMX metabolism. These findings indicated that C6-HSL, as a bacterial QS signal, could enhance microalgal tolerance and antibiotic degradation, offering a novel strategy to improve microalgae-based antibiotic removal in wastewater treatment.

Dredging wastewater discharge caused mangrove sediment antibiotic accumulation and affected functional microbes in carbon and nitrogen metabolism

Antibiotic pollution is a major environmental concern in mariculture activities along coastlines with mangrove forests. However, the content, composition, and ecological impacts of such pollution within mangrove ecosystems have been limitedly explored. In this study, surface sediments and sediment profiles (40 cm deep) were investigated for 14 antibiotics, elemental parameters, and functional gene abundance at mangrove sites affected by dredging wastewater discharge from mariculture ponds along the Jiulong River Estuary. The results revealed that all 14 antibiotics were detected in the surface sediments, with total antibiotics below 6 ng gDW-1 at sites without direct wastewater dicharge. In contrast, sediment profiles from sites receiving wastewater discharge exhibited higher antibiotic contents, reaching up to 19.6 ng gDW-1 in the surface sediments. Fluoroquinolones (ofloxacin and enrofloxacin) were the dominant antibiotic classes of antibiotics, and the deeper sediment layers were also contaminated with antibiotics because of wastewater discharge. Antibiotic accumulation resulting from wastewater discharge significantly affected the functional microbes involved in carbon and nitrogen metabolism. Positive correlations were observed between ofloxacin (florfenicol) and the gene abundance of nosZ and nirK while amoA abundance showed negative correlations. Increased levels of enrofloxacin (terramycin and sulfamethazine), as well as organic carbon and total nitrogen, were associated with higher abundances of narG and mcrA genes. Overall, prolonged wastewater discharge from mariculture activities led to antibiotic accumulation, extending into deep sediment layers, potentially reshaping the functional microbes involved in carbon and nitrogen metabolism. Therefore, future strategies are urgently needed to address antibiotic pollution caused by wastewater discharge near mangrove forests.

Application of iron-modified biochar in the fields of adsorption and degradation of antibiotics

Antibiotics, as emerging contaminants, have led to persistent global pollution issues, prompting long-standing attention on methods for their effective removal. Among various methods, iron-modified biochar stood out for its ability to adsorb and degrade antibiotics in the environment because biochar can provide a porous structure and oxygen-rich functional groups for efficient antibiotic adsorption, while the Fe2+/Fe3+ redox cycle in the iron modification biochar enhanced electronic transmission and further increased degradation. This review systematically summarized preparation methods of different iron-modified biochar, the adsorption capacities, mechanisms, and influencing factors of pollutants. It also explored the co-activation of iron and biochar, which enhanced the release of free radicals through Fenton-like oxidation pathways and accelerated degradation through photocatalytic electron-hole pair production. Additionally, the relationship between adsorption and degradation was discussed. Notably, an environmental risk assessment of iron-modified biochar and disposal of the used iron-modified biochar were discussed, which were critical for practical applications. Finally, the review highlighted the future directions of antibiotic pollution control and the broader potential of iron-modified biochar.

Freeze-thaw effect on adsorption and transport of two sulfonamides in soil: Batch and column studies

Freeze-thaw cycles (FTCs) have significant impacts on soil physicochemical properties, subsequently altering the fate of contaminants in soil. However, studies investigating the environmental behavior of antibiotics in soil subjected to FTCs are limited. This study investigated the effects of FTCs on the adsorption and transport of two commonly used sulfonamide antibiotics (SAs), sulfamethoxazole (SMX) and sulfapyridine (SPY), in soil. The results revealed that FTCs alter the adsorption behavior of SMX and SPY on the soil. Initially, after 1 FTC, the adsorption of both SMX and SPY decreased; however, subsequently, this adsorption gradually increased as the number of FTCs increased. This is because, during the FTCs, the increased soil pH hindered the adsorption of SAs by intensifying electrostatic repulsion between anionic SAs and soil particles. Subsequently, the increases in clay content, specific surface area (SA), small pores, and dissolved organic matter (DOM) provided more adsorption sites, overriding the initial pH effects and ultimately dominating the adsorption process. FTCs altered soil properties, which not only changed the adsorption of SAs but also induced the alteration of pore structure and the generation of preferential flow. During the vertical transport process, such changes in pore pathways played a dominant role, facilitating SMX and SPY transport in soil. The addition of heavy metals (Cd2+ and Cu2+) contributed to facilitating the transport of SMX and SPY in both unfrozen and freeze-thaw-treated soil columns. In the context of global climate change, this study offers valuable insights into the fate and environmental risks associated with pollutants in soil.

Enhancing the removal of sulfamethoxazole and microalgal lipid production through microalgae-biochar hybrids

The use of microalgae for antibiotic removal has received increasing attention due to its many advantages. However, challenges such as limited removal rates and the complexity of algae cell recovery persist. In this study, chitosan and FeCl3 modified peanut shell biochar (CTS@FeBC) was prepared for the immobilization of Chlorella pyrenoidosa. The results showed that CTS@FeBC effectively adsorbed and immobilized microalgal cells to form microalgae-biochar hybrids, resulting in higher sulfamethoxazole removal rate (45.7 %) compared to microalgae (34.4 %) or biochar (20.0 %) alone, and higher microalgal lipid yield (11.6 mg/L d-1) than microalgae alone (10.1 mg/L d-1). More importantly, the microalgae-biochar hybrids could be rapidly separated from the wastewater within 10 min by applying a magnetic field, resulting in a harvesting efficiency of 86.3 %. Overall, the microalgae-biochar hybrids hold great potential in overcoming challenges associated with pollutants removal and microalgal biomass recovery.

Degradation of sulfamethoxazole in a falling film dielectric barrier discharge system: Performance, mechanism and toxicity evaluation

The ubiquitous presence of sulfonamides (SAs) in wastewater poses serious risks to human health and ecosystem safety. This study evaluated the performance of a falling film dielectric barrier discharge (DBD) system on the removal of five SAs, namely sulfamethoxazole (SMX), sulfisoxazole (SIZ), sulfathiazole (STZ), sulfadiazine (SDZ) and sulfamerazine (SMR). Removal efficiencies >99 % were observed for all target SAs within 30 min of treatment, with pseudo-first order rate constants varying between 0.17 and 0.27 min-1. Superior removal efficiencies were achieved under acidic conditions compared to neutral and alkaline conditions. Using SMX as a model compound, mechanistic investigations revealed that the synergy of reactive oxygen species (ROS) and reactive nitrogen species (RNS) led to its efficient degradation, with peroxynitrites (ONOO-/ONOOH) and hydroxyl radical (OH) playing pivotal roles. SMX degradation pathways encompassing nitration/nitrosation, hydroxylation, deamination, CS and SN bond cleavage were proposed. The toxicity evaluation results demonstrated that the solution toxicity diminished following the plasma treatment under specific conditions. In particular, the solution treated with air or oxygen discharge enhanced the growth of wheat seedlings, suggesting the potential for reusing plasma-treated wastewater in agriculture. This study enhances our understanding of the underlying mechanisms involved in the plasma degradation of SAs and reveals the significant potential of plasma technology as a sustainable approach for treating wastewater.

Understanding the role of microbes in health and disease of farmed aquatic organisms

Aquaculture is critical to reduce protein deficiencies and supplement the world's demand for seafood. However, the culture environment predisposes farmed animals to infectious diseases. In particular, the high density of fish, crustacean, mollusk, sea cucumber or algal species allows for the rapid spread of infectious diseases resulting in devastating losses. Massive amounts of antibiotics have been used to sustain aquaculture production. This has led to the critical need to evaluate the impact of current control measures and optimize disease management schemes with an emphasis on global impact and sustainability. Furthermore, local and global changes have enhanced the pathogens' effects over aquaculture settings because increased temperature and pollution may trigger virulence genes and toxin production. Technological developments including biofloc technology, integrated multitrophic systems, recirculating aquaculture systems and probiotics have contributed to enhancing aquaculture sustainability and reducing the need for high loads of antibiotics and other chemicals. Furthermore, biotechnological tools (e.g., omics and cell biology) have shed light on cellular processes in the health and disease of reared organisms. Metagenomics is a reliable and relatively quick tool to identify microbial communities in aquaculture settings.

Fluoroquinolone antibiotics in the aquatic environment: environmental distribution, the research status and eco-toxicity

The increasing presence of fluoroquinolone (FQ) antibiotics in aquatic environments is a growing concern due to their widespread use, negatively impacting aquatic organisms. This paper provides an overview of the environmental distribution, sources, fate, and both single and mixed toxicity of FQ antibiotics in aquatic environments. It also examines the accumulation of FQ antibiotics in aquatic organisms and their transfer into the human body through the food chain. The study identifies critical factors such as metabolism characteristics, physiochemical characteristics, light, temperature, dissolved oxygen, and environmental compatibility that influence the presence of FQ antibiotics in aquatic environments. Mixed pollutants of FQ antibiotics pose significant risks to the ecological environment. Additionally, the paper critically discusses advanced treatment technologies designed to remove FQ antibiotics from wastewater, focusing on advanced oxidation processes (AOPs) and electrochemical advanced oxidation processes (EAOPs). The discussion also includes the benefits and limitations of these technologies in degrading FQ antibiotics in wastewater treatment plants. The paper concludes by proposing new approaches for regulating and controlling FQ antibiotics to aid in the development of ecological protection measures.

Bacterial cellulose-supported dual-layered nanofibrous adsorbent for thin-film micro-solid-phase extraction of antibiotics in municipal wastewaters

In this study, bacterial cellulose was coated with composite nanofibers of polyvinyl alcohol doped with beta cyclodextrin and alginate (PVA-SA-βCD), constructed using the electrospinning technique. This novel material served as an effective adsorbent for thin-film micro-solid-phase extraction (TF-μSPE) of antibiotics from water samples, followed by HPLC-UV analysis. The adsorbent was subjected to a comprehensive characterization using ATR-FTIR, FE-SEM, and BET techniques. These analyses provided valuable insights into its physicochemical structure and properties. Several key parameters that affect the performance of the TF-μSPE method were investigated including electrospinning factors (voltage, flow rate, needle tip-collector distance, and electrospinning time), desorption solvent type and volume, adsorbent dose, adsorption and desorption times, pH value, and salt percentage. Under the optimized conditions, the limits of detections and quantifications for target antibiotics were obtained in the ranges of 0.02-0.03 and 0.07-0.1 μg L⁻1, respectively. The linear range was 0.07-1000 μg L⁻1 with satisfactory determination coefficients (r2) of 0.9944-0.9984. The intra-day and inter-day precisions were obtained as 1.1-1.7 % and 2.2-3.5 %, respectively. The developed method was successfully applied to determine antibiotics in municipal wastewater samples, yielding recoveries within the range of 70-100 % (RSD%<3.7). The green features of the method were also assessed based on AGREE tool. This is the first report on the fabrication of a double-layered nanofibrous adsorbent and its application for the adsorption of antibiotics in wastewater. This robust approach combines efficiency with analytical accuracy, making it a valuable tool for antibiotic analysis in environmental samples.

Distinct electrochemical and metabolic responses of anode respiring bacteria to sulfamethoxazole in microbial fuel cells coupled with constructed wetlands

The influence of sulfamethoxazole (SMX) on the electrochemical activity, bacterial community, and metabolic state of anode respiring microbes was investigated in constructed-wetland-coupled microbial fuel cells (CW-MFCs). Results suggested that SMX shortened the acclimatisation period and enhanced the maximal power density of the CW-MFC at 0.1 mg/L. Cyclic voltammetry (CV) results indicated that SMX may trigger an electrocatalytic process related to an extra redox-active compound. Exposure to SMX significantly altered the bacterial communities, leading to decreased abundances of Desulfurivibrio and Pseudomonas, while increasing the contents of Rhodobacter and Anaerovorax. Furthermore, metabolites related to amino acids and nucleotide metabolism were suppressed at 10 mg/L SMX, while the related metabolites increased at 0.1 mg/L SMX. The upregulated pathway of biofilm formation indicated that the bacteria tended to form biofilms under the influence of SMX. This study provides valuable insights into the complex interactions between SMX and electrochemically active bacteria.

Isolation and Characterization of a Novel Vibrio Phage vB_ValA_R15Z

Vibrio phages have emerged as a potential alternative to antibiotic therapy for treating Vibrio infections. In this study, a lytic Vibrio phage, vB_ValA_R15Z against Vibrio alginolyticus ATCC 17749T, was isolated from an aquatic water sample collected in Xiamen, China. The phage had an icosahedral head (diameter 69 ± 2 nm) and a short, non-contractile tail measuring 16 ± 2 nm. The genome of vB_ValA_R15Z was found to be a double-stranded DNA consisting of 43, 552 bp, containing 54 coding sequences (CDSs) associated with phage packaging, structure, DNA metabolism, lysis and additional functions. The BLASTN results indicated that vB_ValA_R15Z shared less than 90.18% similarity with known phages recorded in the NCBI GenBank database, suggesting that vB_ValA_R15Z was a novel Vibrio phage. Furthermore, phylogenetic analysis revealed that vB_ValA_R15Z belongs to the genus Kaohsiungvirus. In addition, a typical lytic mechanism (holin-endolysim) was found in the genome of vB_ValA_R15Z, while no antibiotic resistance- or virulence factor-related gene was detected. Overall, the study provides valuable insights into the isolation and characterization of vB_ValA_R15Z, highlighting its potential as an effective phage therapy option for combating Vibrio alginolyticus infections.

Ecological risk assessment of commonly used antibiotics in aquatic ecosystems along the coast of China

The consistent input of antibiotics into aquatic environments may pose risks to various creatures and ecosystems. However, risk assessment of pharmaceuticals and personal care products (PPCPs) in aquatic environments is frequently limited by the lack of toxicity data. To investigate the risk of commonly used antibiotics to various aquatic creatures, we focused on the distribution patterns and temporal dynamics of antibiotics in the coastal estuary area of China and performed a comprehensive ecological risk assessment for four antibiotics: erythromycin (ERY), tetracycline (TCN), norfloxacin (NOR) and sulfamethoxazole (SMX). An interspecies correlation estimation (ICE)-species sensitivity distribution (SSD) combined model was applied to predict the toxicity data of untested aquatic species, and an accurate ecological risk assessment procedure was developed to evaluate the risk level of PPCPs. The results of risk quotient assessments and probabilistic risk assessments (PRAs) suggested that four objective antibiotics in the Chinese coastal estuary area were at a low risk level. These antibiotics posed a high risk in antibiotic-related global hot spots, with probabilistic risk values for ERY, NOR, SMX, and TCN of 81.33 %, 27.08 %, 21.13 %, and 15.44 %, respectively. We applied an extrapolation method to overcome the lack of toxicity data in ecological risk assessment, enhanced the ecological reality of water quality criteria derivation and reduced the uncertainty of risk assessment for antibiotics.

Exploring the efficiency of tide flow constructed wetlands for treating mariculture wastewater: A comprehensive study on antibiotic removal mechanism under salinity stress

Antibiotic residues in aquaculture environment pose persistent threats to ecology and human health, exacerbated by salt-alkali mariculture wastewater. Yet, little is known about antibiotic removal in tidal flow constructed wetlands (TFCWs) under salinity stress, especially considering TFCW constitution, configuration, and influent water characteristics. Here, the removal performance and mechanism of different TFCWs for sulfonamide antibiotics (SAs: sulfadiazine, sulfamethazine, sulfamonomethoxine, and sulfamethoxazole) and trimethoprim (TMP) from mariculture wastewater (with low, medium, and high salinity) were evaluated alongside comparisons of environmental factors and microbial responses. Results showed substantial reduction in alkalinity (from 8.25-8.26 to 7.65-8.18), salinity (from 3.67-11.30 ppt to 3.20-10.79 ppt), and SAs concentrations (from 7.79-15.46 mg/L to 0.25-10.00 mg/L) for mariculture wastewater using TFCWs. Zeolite and yellow flag configurations exhibited superior performance in SAs removal from mariculture wastewater. Furthermore, the salt-alkali neutralization and oxygen transport capabilities of zeolite, along with the salt-alkali tolerance and biofilm formation characteristics of yellow flag, promoted the development of a biofilm in the rhizosphere dominated by oxidative stress tolerance and facultative anaerobic traits, thereby improving the TFCW microenvironment. Consequently, aerobic (Sulfuritalea and Enterobacter) and salt-tolerant (Pseudomonas) functional bacteria involved in antibiotic degradation were selectively enriched in the zeolite- and yellow flag-TFCWs, contributing to the effective biodegradation of SAs (achieving removal efficiency of 92-97 %). Besides, the high salt-alkali levels of mariculture wastewater and the strong oxygen-enriched capacity of the TFCWs not only enhanced the aerobic oxidation reaction of SAs, but also bidirectionally inhibited the substrate adsorption and anaerobic reduction process of TMP. These findings address a critical gap by investigating the efficacy of TFCWs in removing antibiotics from mariculture wastewater under various salinity conditions, providing essential insights for optimizing wetland design and improving wastewater management in mariculture environments.

Molecular insights into linkages among free-floating macrophyte-derived organic matter, the fate of antibiotic residues, and antibiotic resistance genes

Macrophyte rhizospheric dissolved organic matter (ROM) served as widespread abiotic components in aquatic ecosystems, and its effects on antibiotic residues and antibiotic resistance genes (ARGs) could not be ignored. However, specific influencing mechanisms for ROM on the fate of antibiotic residues and expression of ARGs still remained unclear. Herein, laboratory hydroponic experiments for water lettuce (Pistia stratiotes) were carried out to explore mutual interactions among ROM, sulfamethoxazole (SMX), bacterial community, and ARGs expression. Results showed ROM directly affect SMX concentrations through the binding process, while CO and N-H groups were main binding sites for ROM. Dynamic changes of ROM molecular composition diversified the DOM pool due to microbe-mediated oxidoreduction, with enrichment of heteroatoms (N, S, P) and decreased aromaticity. Microbial community analysis showed SMX pressure significantly stimulated the succession of bacterial structure in both bulk water and rhizospheric biofilms. Furthermore, network analysis further confirmed ROM bio-labile compositions as energy sources and electron shuttles directly influenced microbial structure, thereby facilitating proliferation of antibiotic resistant bacteria (Methylotenera, Sphingobium, Az spirillum) and ARGs (sul1, sul2, intl1). This investigation will provide scientific supports for the control of antibiotic residues and corresponding ARGs in aquatic ecosystems.

A Review on Fluoroquinolones' Toxicity to Freshwater Organisms and a Risk Assessment

Fluoroquinolones (FQs) have achieved significant success in both human and veterinary medicine. However, regulatory authorities have recommended limiting their use, firstly because they can have disabling side effects; secondly, because of the need to limit the spread of antibiotic resistance. This review addresses another concerning consequence of the excessive use of FQs: the freshwater environments contamination and the impact on non-target organisms. Here, an overview of the highest concentrations found in Europe, Asia, and the USA is provided, the sensitivity of various taxa is presented through a comparison of the lowest EC50s from about a hundred acute toxicity tests, and primary mechanisms of FQ toxicity are described. A risk assessment is conducted based on the estimation of the Predicted No Effect Concentration (PNEC). This is calculated traditionally and, in a more contemporary manner, by constructing a normalized Species Sensitivity Distribution curve. The lowest individual HC5 (6.52 µg L-1) was obtained for levofloxacin, followed by ciprofloxacin (7.51 µg L-1), sarafloxacin and clinafloxacin (12.23 µg L-1), and ofloxacin (17.12 µg L-1). By comparing the calculated PNEC with detected concentrations, it is evident that the risk cannot be denied: the potential impact of FQs on freshwater ecosystems is a further reason to minimize their use.

A meta-analysis of antibiotic residues in the Beibu Gulf

Antibiotic residue stands as a significant ongoing environmental issue, with aquaculture being a major source of annual antibiotic discharge into the ocean. Nevertheless, there is still an incomplete evaluation of antibiotic residues in the Beibu Gulf, an area encompassed by two prominent aquaculture nations, China and Vietnam. The present systematic review and meta-analysis was conducted to examine the presence antibiotic residues in the Beibu Gulf based on published studies. Data were obtained through eight databases up to December 19th, 2023, and were updated on April 15th, 2024. The pooled concentration of antibiotic residues in seawater was 5.90 (ng/L), ranging from 5.73 to 6.06 (ng/L), and was 8.03 (ng/g), ranging from 7.77 to 8.28 (ng/g) in sediments. Fluoroquinolones, tetracyclines, and macrolides were identified as the main antibiotics found in both seawater and sediment samples. The Beibu Gulf showed higher antibiotic levels in its western and northeastern areas. Additionally, the nearshore mangrove areas displayed the highest prevalence of antibiotic residues. It is strongly advised to conduct regular long-term monitoring of antibiotic residues in the Beibu Gulf. Collaborative surveys covering the entire Beibu Gulf involving China and Vietnam are recommended.

Effects of sulfamonomethoxine and trimethoprim co-exposures at different environmentally relevant concentrations on microalgal growth and nutrient assimilation

In aquaculture around the world, sulfamonomethoxine (SMM), a long-acting antibiotic that harms microalgae, is widely employed in combination with trimethoprim (TMP), a synergist. However, their combined toxicity to microalgae under long-term exposures at environmentally relevant concentrations remains poorly understood. Therefore, we studied the effects of SMM single-exposures and co-exposures (SMM:TMP=5:1) at concentrations of 5 μg/L and 500 μg/L on Chlorella pyrenoidosa within one aquacultural drainage cycle (15 days). Photosynthetic activity and N assimilating enzyme activities were employed to evaluate microalgal nutrient assimilation. Oxidative stress and flow cytometry analysis for microalgal proliferation and death jointly revealed mechanisms of inhibition and subsequent self-adaptation. Results showed that exposures at 5 μg/L significantly inhibited microalgal nutrient assimilation and induced oxidative stress on day 7, with a recovery to levels comparable to the control by day 15. This self-adaptation and over 95 % removal of antibiotics jointly contributed to promoting microalgal growth and proliferation while reducing membrane-damaged cells. Under 500 μg/L SMM single-exposure, microalgae self-adapted to interferences on nutrient assimilation, maintaining unaffected growth and proliferation. However, over 60 % of SMM remained, leading to sustained oxidative stress and apoptosis. Remarkably, under 500 μg/L SMM-TMP co-exposure, the synergistic toxicity of SMM and TMP significantly impaired microalgal nutrient assimilation, reducing the degradation efficiency of SMM to about 20 %. Consequently, microalgal growth and proliferation were markedly inhibited, with rates of 9.15 % and 17.7 %, respectively, and a 1.36-fold increase in the proportion of cells with damaged membranes was observed. Sustained and severe oxidative stress was identified as the primary cause of these adverse effects. These findings shed light on the potential impacts of antibiotic mixtures at environmental concentrations on microalgae, facilitating responsible evaluation of the ecological risks of antibiotics in aquaculture ponds.

Fate of sulfamethoxazole in wetland sediment under controlled redox conditions

Redox condition is an important controlling factor for contaminant removal in constructed wetlands; however, the redox-sensitivity of antibiotic removal in wetland sediments under controlled conditions with specific electron acceptors remains unclear. Here, using a 14C radioactive tracer, we explored fate of sulfamethoxazole (SMX) in a wetland sediment slurry under oxic, nitrate-reducing, iron-reducing, and methanogenic conditions. In the sterile treatment, unlike the comparable SMX dissipation from the water phase under four redox conditions, non-extractable residues (NERs) of SMX was highest formed in the sediment under oxic condition, mainly in sequestered and ester/amide-linked forms. Microorganisms markedly promoted SMX transformation in the slurry. The dissipation rate of SMX and its transformation products (TPs) followed the order: oxic ≈ iron-reducing > methanogenic >> nitrate-reducing conditions, being consistent with the dynamics of microbial community in the sediment, where microbial diversity was greater and networks connectivity linking dominant bacteria to SMX transformation were more complex under oxic and iron-reducing conditions. Kinetic modeling indicated that the transformation trend of SMX and its TPs into the endpoint pool NERs depended on the redox conditions. Addition of wetland plant exudates and sediment dissolved organic matter at environmental concentrations affected neither the abiotic nor the biotic transformation of SMX. Overall, the iron-reducing condition was proven the most favorable and eco-friendly for SMX transformation, as it resulted in a high rate of SMX dissipation from water without an increase in toxicity and subsequent formation of significant stable NERs in sediment. Our study comprehensively revealed the abiotic and biotic transformation processes of SMX under controlled redox conditions and demonstrated iron-reducing condition allowing optimal removal of SMX in constructed wetlands.

Physiological-biochemical responses and transcriptomic analysis reveal the effects and mechanisms of sulfamethoxazole on the carbon fixation function of Chlorella pyrenoidosa

The occurrence of sulfamethoxazole (SMX) is characterized by low concentration and pseudo-persistence. However, the toxic effects and mechanisms of SMX, especially for low concentration and long-term exposure, are still not clear. This study investigated the effects and mechanisms of SMX on carbon fixation-related biological processes of Chlorella pyrenoidosa at population, physiological-biochemical, and transcriptional levels. Results showed that 1-1000 μg/L SMX significantly inhibited the dry weight and carbon fixation rate of C. pyrenoidosa during 21 d. The upregulation of superoxide dismutase (SOD) and catalase (CAT) activities, as well as the accumulation of malondialdehyde (MDA) demonstrated that SMX posed oxidative damage to C. pyrenoidosa. SMX inhibited the activity of carbonic anhydrase (CA), and consequently stimulated the activity of Rubisco. Principal component analysis (PCA) revealed that SMX concentration was positively correlated with Rubisco and CAT while exposure time was negatively correlated with CA. Transcriptional analysis showed that the synthesis of chlorophyll-a was stabilized by regulating the diversion of protoporphyrin IX and the chlorophyll cycle. Meanwhile, multiple CO2 compensation mechanisms, including photorespiratory, C4-like CO2 compensation and purine metabolism pathways were triggered in response to the CO2 requirements of Rubisco. This study provides a scientific basis for the comprehensive assessment of the ecological risk of SMX.

Synergistic Control of Trimethoprim and the Antimicrobial Resistome in Electrogenic Microbial Communities

Synergistic control of the risks posed by emerging antimicrobials and antibiotic resistance genes (ARGs) is crucial for ensuring ecological safety. Although electrogenic respiration can enhance the biodegradation of several antimicrobials and reduce ARGs accumulation, the association mechanisms of antimicrobial biodegradation (trimethoprim, TMP) with the fate of the antimicrobial resistome remain unclear. Here, the biotransformation pathway of TMP, microbial associations, and functional gene profiles (e.g., degradation, antimicrobial resistance, and electron transfer) were analyzed. The results showed that the microbial electrogenic respiration significantly enhanced the biodegradation of TMP, especially with a cosubstrate sodium acetate supply. Electroactive bacteria enriched in the electrode biofilm positively correlated with potential TMP degraders dominated in the planktonic communities. These cross-niche microbial associations may contribute to the accelerated catabolism of TMP and extracellular electron transfer. Importantly, the evolution and dissemination of overall ARGs and mobile genetic elements (MGEs) were significantly weakened due to the enhanced cometabolic biodegradation of TMP. This study provides a promising strategy for the synergistic control of the water ecological risks of antimicrobials and their resistome, while also highlighting new insights into the association of antimicrobial biodegradation with the evolution of the resistome in an electrically integrated biological process.

Environmental remediation of the norfloxacin in water by adsorption: Advances, current status and prospects

Antibiotics are considered as the new generation water pollutants as these disturb endocrine systems if water contaminated with antibiotics is consumed. Among many antibiotics norfloxacin is present in various natural water bodies globally. This antibiotic is considered an emerging pollutant due to its low degradation in aquatic animals. Besides, it has many side effects on human vital organs. Therefore, the present article discusses the recent advances in the removal of norfloxacin by adsorption. This article describes the presence of norfloxacin in natural water, consumption, toxicity, various adsorbents for norfloxacin removal, optimization factors for norfloxacin removal, kinetics, thermodynamics, modeling, adsorption mechanism and regeneration of the adsorbents. Adsorption takes place in a monolayer following the Langmuir model. The Pseudo-second order model represents the kinetic data. The adsorption capacity ranged from 0.924 to 1282 mg g-1. In this sense, the parameters such as the NFX concentration added to the adsorbent textural properties exerted a great influence. Besides, the fixed bed-based removal at a large scale is also included. In addition to this, the simulation studies were also discussed to describe the adsorption mechanism. Finally, the research challenges and future perspectives have also been highlighted. This article will be highly useful for academicians, researchers, industry persons, and government authorities for designing future advanced experiments.

Strain-level diversity in sulfonamide biodegradation: adaptation of Paenarthrobacter to sulfonamides

The widespread occurrence of sulfonamides raises significant concerns about the evolution and spread of antibiotic resistance genes. Biodegradation represents not only a resistance mechanism but also a clean-up strategy. Meanwhile, dynamic and diverse environments could influence the cellular function of individual sulfonamide-degrading strains. Here, we present Paenarthrobacter from different origins that demonstrated diverse growth patterns and sulfonamide-degrading abilities. Generally, the degradation performance was largely associated with the number of sadA gene copies and also relied on its genotype. Based on the survey of sad genes in the public database, an independent mobilization of transposon-borne genes between chromosome and plasmid was observed. Insertions of multiple sadA genes could greatly enhance sulfonamide-degrading performance. Moreover, the sad gene cluster and sadA transposable element showed phylogenetic conservation currently, being identified only in two genera of Paenarthrobacter (Micrococcaceae) and Microbacterium (Microbacteriaceae). Meanwhile, Paenarthrobacter exhibited a high capacity for genome editing to adapt to the specific environmental niche, opening up new opportunities for bioremediation applications.

Sulfamethoxazole removal from wastewater via anoxic/oxic moving bed biofilm reactor: Degradation pathways and toxicity assessment

The effects of sulfamethoxazole (SMZ), an antibiotic commonly detected in the water environment, on the performance of a single staged anoxic/oxic moving bed biofilm reactor (A/O MBBR), was investigated. The anoxic zone played a key role in the removal of SMZ with a percentage of contribution accounting for around 85% in the overall removal. Denitrifying heterotrophic microbes present in the anoxic zone showed relatively more resistance to higher SMZ loads. It was found that in extracellular polymeric substances, protein content was increased consistently with the increase in SMZ concentration. Based on the detected biotransformation products, four degradation pathways were proposed and the toxicity was evaluated. Metagenomic analysis revealed that at higher SMZ load the activity of genera, such as Proteobacteria and Actinobacteria was significantly affected. In summary, proper design and operation of staged A/O MBBR can offer a resilient and robust treatment towards SMZ removal from wastewater.

Comprehensive assessment of toxicity and environmental risk associated with sulfamethoxazole biodegradation in sulfur-mediated biological wastewater treatment

Incomplete mineralization of sulfamethoxazole (SMX) in wastewater treatment systems poses a threat to ecological health. The toxicity and environmental risk associated with SMX biodegradation in the sulfur-mediated biological process were examined for the first time through a long-term (180 days) bioreactor study and a series of bioassays. The results indicated that the sulfur-mediated biological system was highly resistant and tolerant to SMX toxicity, as evidenced by the enrichment of sulfate-reducing bacteria (SRB), the improved microbial metabolic activity, and the excellent performance on pollutants removal under long-term SMX exposure. SMX can be effectively biodegraded by the cleavage and rearrangement of the isoxazole ring, hydrogenation and hydroxylation reactions in sulfur-mediated biological wastewater system. These biodegradation pathways effectively reduced the acute toxicity, antibacterial activity, and ecotoxicities of SMX and its biotransformation products (TPs) in the effluent of the sulfur-mediated biological system. The TPs produced via hydrogenation (TP1), hydroxylation, and isoxazole ring cleavage (TP3, TP4, TP5, TP8, and TP9) exhibited lower toxicity than SMX. Under SMX stress, although the abundance of sulfonamide resistance genes increased, the total abundance of ARGs decreased due to the extrusion of some intracellular SMX by the efflux pump genes and the inactivation of some SMX through the biodegradation process. Efflux pump and inactivation, as the main resistance mechanisms of antibiotics in the sulfur-mediated biological system, play a crucial role in microbial self-defense. The findings of this study demonstrate the great potential of the sulfur-mediated biological system in SMX removal, detoxication, and ARGs environmental risk reduction.

Epigenetic Modulations for Prevention of Infectious Diseases in Shrimp Aquaculture

Aquaculture assumes a pivotal role in meeting the escalating global food demand, and shrimp farming, in particular, holds a significant role in the global economy and food security, providing a rich source of nutrients for human consumption. Nonetheless, the industry faces formidable challenges, primarily attributed to disease outbreaks and the diminishing efficacy of conventional disease management approaches, such as antibiotic usage. Consequently, there is an urgent imperative to explore alternative strategies to ensure the sustainability of the industry. In this context, the field of epigenetics emerges as a promising avenue for combating infectious diseases in shrimp aquaculture. Epigenetic modulations entail chemical alterations in DNA and proteins, orchestrating gene expression patterns without modifying the underlying DNA sequence through DNA methylation, histone modifications, and non-coding RNA molecules. Utilizing epigenetic mechanisms presents an opportunity to enhance immune gene expression and bolster disease resistance in shrimp, thereby contributing to disease management strategies and optimizing shrimp health and productivity. Additionally, the concept of epigenetic inheritability in marine animals holds immense potential for the future of the shrimp farming industry. To this end, this comprehensive review thoroughly explores the dynamics of epigenetic modulations in shrimp aquaculture, with a particular emphasis on its pivotal role in disease management. It conveys the significance of harnessing advantageous epigenetic changes to ensure the long-term viability of shrimp farming while deliberating on the potential consequences of these interventions. Overall, this appraisal highlights the promising trajectory of epigenetic applications, propelling the field toward strengthening sustainability in shrimp aquaculture.

New insight into the concentration-dependent removal of multiple antibiotics by Chlorella sorokiniana

Microalgae have attracted increasing attention as an environmentally friendly treatment for antibiotics. However, the effect of antibiotic concentration on the removal ability of microalgae with the underlying mechanisms remains unclear. Thus, this work investigates the removal of tetracycline (TET), sulfathiazole (STZ), and ciprofloxacin (CIP) at different concentrations using Chlorella sorokiniana. The results indicate that microalgae have a concentration-dependent effect on antibiotic removal; however, the removal trends for the three antibiotics differed significantly. Specifically, TET showed nearly 100% removal efficiency at any concentration. The high concentration of STZ inhibited microalgal photosynthesis and induced the production of ROS, leading to antioxidant damage and inhibiting removal efficiency. Conversely, CIP enhanced the ability of microalgae to remove CIP by inducing a dual peroxidase and cytochrome p450 enzyme response. Furthermore, the economic analysis demonstrated that microalgae treatment antibiotics were calculated to be 4.93€/m³, which becomes cheaper than the other microalgae water treatment process.

Effect of resistance difference on distribution of antibiotics in bacterial cell and conjugative gene transfer risks during electrochemical flow through reaction

The occurrences and spread of antibiotic resistance (AR) mediated by horizontal gene transfer (HGT) of antibiotic resistance genes (ARGs) in aquatic environment have been aggravated because of the abuse of antibiotics. While the pressure of different antibiotics is known to induce the spread of AR in bacteria, whether distribution of different antibiotics in cell structure could affect HGT risks is not clear. Here, a significant difference between the distribution of tetracycline hydrochloride (Tet) and sulfamethoxazole (Sul) in cell structure during electrochemical flow through reaction (EFTR) process was firstly reported. Meanwhile, EFTR treatment possessed excellent disinfection performance and consequently controlled the HGT risks. The intracellular Tet (iTet) was discharged through efflux pumps to increase the content of extracellular Tet (eTet) due to the resistance of donor E. coli DH5α under the selective pressure of Tet, declining the damage of donor and plasmid RP4. The HGT frequency was 8.18-fold increase compared with that by EFTR treatment alone. While the secretion of intracellular Sul (iSul) was inhibited by blocking the formation of efflux pumps to inactivate the donor under the Sul pressure, and the total content of iSul and adsorbed Sul (aSul) to be 1.36-fold higher than that of eSul. Therefore, the reactive oxygen species (ROS) generation and cell membrane permeability were improved to release ARGs, and •OH attacked plasmid RP4 in the EFTR process, inhibiting the HGT risks. This study advances the awareness of the interaction between distribution of different antibiotics in cell structure and the HGT risks in the EFTR process.

Spatial variability, source identification and risks assessment of antibiotics in multimedia of North China's largest freshwater lake using positive matrix factorization and Monte Carlo simulation

Antibiotics are widely found in aquatic ecosystems and pose a serious threat to human and the ecological system. Samples of surface water (SW), overlying water (OW), pore water (PW) and sediments (Sedi) were collected to investigate the spatial variability, potential sources, ecological risk (RQs) and health risks (HQs) of nine common antibiotics in Baiyangdian Lake using positive matrix factorization (PMF), and Monte Carlo simulation. Significant spatial autocorrelation of most antibiotics were observed in PW and Sedi samples rather than in SW and OW samples, and higher antibiotic levels were found in the northwest of waters and the southwest of sediments. Livestock (26.74-35.57%) and aquaculture (21.62-37.70%) were identified as primary sources of antibiotics in the water and sediments. Norfloxacin and roxithromycin showed high levels of RQ and HQ in more than 50% of samples, respectively. The combined RQ (ΣRQ) in the PW can be used as a sign of across multimedia risk. Notably, appreciable health risks were observed for the combined HQ (ΣHQ) in about 80% of samples, indicating the importance of taking health risk of antibiotics into consideration. The findings of this work provides a reference for antibiotics pollution control and risk management in shallow lake.

An In Vivo Whole-Transcriptomic Approach to Assess Developmental and Reproductive Impairments Caused by Flumequine in Daphnia magna

Among veterinary antibiotics, flumequine (FLU) is still widely used in aquaculture due to its efficacy and cost-effectiveness. Although it was synthesized more than 50 years ago, a complete toxicological framework of possible side effects on non-target species is still far from being achieved. The aim of this research was to investigate the FLU molecular mechanisms in Daphnia magna, a planktonic crustacean recognized as a model species for ecotoxicological studies. Two different FLU concentrations (2.0 mg L-1 and 0.2 mg L-1) were assayed in general accordance with OECD Guideline 211, with some proper adaptations. Exposure to FLU (2.0 mg L-1) caused alteration of phenotypic traits, with a significant reduction in survival rate, body growth, and reproduction. The lower concentration (0.2 mg L-1) did not affect phenotypic traits but modulated gene expression, an effect which was even more evident under the higher exposure level. Indeed, in daphnids exposed to 2.0 mg L-1 FLU, several genes related with growth, development, structural components, and antioxidant response were significantly modulated. To the best of our knowledge, this is the first work showing the impact of FLU on the transcriptome of D. magna.

A Review of Antibiotics, Antibiotic Resistant Bacteria, and Resistance Genes in Aquaculture: Occurrence, Contamination, and Transmission

Antibiotics are commonly used to prevent and control diseases in aquaculture. However, long-term/overuse of antibiotics not only leaves residues but results in the development of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Antibiotics, ARB, and ARGs are widespread in aquaculture ecosystems. However, their impacts and interaction mechanisms in biotic and abiotic media remain to be clarified. In this paper, we summarized the detection methods, present status, and transfer mechanisms of antibiotics, ARB, and ARGs in water, sediment, and aquaculture organisms. Currently, the dominant methods of detecting antibiotics, ARB, and ARGs are UPLC-MS/MS, 16S rRNA sequencing, and metagenomics, respectively. Tetracyclines, macrolides, fluoroquinolones, and sulfonamides are most frequently detected in aquaculture. Generally, antibiotic concentrations and ARG abundance in sediment are much higher than those in water. Yet, no obvious patterns in the category of antibiotics or ARB are present in organisms or the environment. The key mechanisms of resistance to antibiotics in bacteria include reducing the cell membrane permeability, enhancing antibiotic efflux, and structural changes in antibiotic target proteins. Moreover, horizontal transfer is a major pathway for ARGs transfer, including conjugation, transformation, transduction, and vesiculation. Identifying, quantifying, and summarizing the interactions and transmission mechanisms of antibiotics, ARGs, and ARB would provide useful information for future disease diagnosis and scientific management in aquaculture.

The different toxicological effects and removal efficiencies of norfloxacin and sulfadiazine in culturing Arthrospira (Spirulina) platensis

Norfloxacin (NFX) and sulfadiazine (SDZ) are two widely used antibiotics belonging to fluoroquinolone and sulfonamide groups, respectively, and have become the commonly detected micropollutants in aquatic environments. However, only few works have been conducted to investigate the highly probable inhibition of these antibiotic pollutants to Arthrospira platensis, which is an important species of cyanobacteria that is one of primary producers in aquatic ecosystems and should be remarkably sensitive to environmental pollutants due to its prokaryotic characteristics. Hence, the toxicological effects and removal efficiencies of NFX and SDZ in culturing A. platensis were studied by analyzing the biomass growth, photosynthetic pigments, primary biocomponents, and antibiotics concentration. The corresponding variations of these characteristics showed the higher sensitivity of A. platensis to NFX than to SDZ, indicating the specifically targeted effect of NFX on A. platensis, which could be confirmed in silico by the higher binding affinity of NFX with the critical enzyme. The obtained results illustrated the roles of NFX and SDZ on the growth of A. platensis, thus providing the great support in employing A. platensis to reduce hazards from contaminated water and recover biomass resources.

Mangrove microbial community recovery and their role in early stages of forest recolonization within shrimp ponds

Shrimp farming is blooming worldwide, posing a severe threat to mangroves and its multiple goods and ecosystem services. Several studies reported the impacts of aquaculture on mangrove biotic communities, including microbiomes. However, little is known about how mangrove soil microbiomes would change in response to mangrove forest recolonization. Using genome-resolved metagenomics, we compared the soil microbiome of mangrove forests (both with and without the direct influence of shrimp farming effluents) with active shrimp farms and mangroves under a recolonization process. We found that the structure and composition of active shrimp farms microbial communities differ from the control mangrove forests, mangroves under the impact of the shrimp farming effluents, and mangroves under recolonization. Shrimp farming ponds microbiomes have lower microbial diversity and are dominated by halophilic microorganisms, presenting high abundance of multiple antibiotic resistance genes. On the other hand, control mangrove forests, impacted mangroves (exposed to the shrimp farming effluents), and recolonization ponds were more diverse, with a higher abundance of genes related to carbon mobilization. Our data also indicated that the microbiome is recovering in the mangrove recolonization ponds, performing vital metabolic functions and functionally resembling microbiomes found in those soils of neighboring control mangrove forests. Despite highlighting the damage caused by the habitat changes in mangrove soil microbiome community and functioning, our study sheds light on these systems incredible recovery capacity. Our study shows the importance of natural mangrove forest recovery, enhancing ecosystem services by the soil microbial communities even in a very early development stage of mangrove forest, thus encouraging mangrove conservation and restoration efforts worldwide.

Source-specific ecological risks and critical source identification of PPCPs in surface water: Comparing urban and rural areas

To control the concentrations of pharmaceutical and personal care products (PPCPs) in the surface water of urban and rural areas, it is important to explore the spatial variation in source-specific ecological risks and identify critical sources. Here, we focused on 22 PPCPs found in the effluent from wastewater treatment plants and surface water in Tianjin, and source-specific risk was quantitatively apportioned combining positive matrix factorization with ecological risk assessment. Results showed that rural areas exhibited a more severe contamination level than urban areas. Medical wastewater (30.1 %) accounted for the highest proportion, while domestic sewage posed the greatest threat to aquatic ecosystems. The incidence of potential risks (RQ > 0.01) caused by domestic sewage in urban areas (88.9 %) was higher than that in rural areas (75.9 %). However, PPCP risks caused by farmland drainage, aquaculture, and livestock discharge were mainly distributed in rural areas. The critical source identified in the entire region was domestic sewage (weight, 0.36), and its weight (0.51) in urban areas was greater than that in rural areas (0.32). The impact of aquaculture (weight, 0.16) in rural areas was noteworthy. These findings may contribute to developing environmental management strategies in key areas to help alleviate PPCP contamination worldwide.

Quinolone distribution, trophodynamics, and human exposure risk in a transit-station lake for water diversion in east China

Quinolone antibiotics (QNs) pollution in lake environments is increasingly raising public concern due to their potential combined toxicity and associated risks. However, the spatiotemporal distribution and trophodynamics of QNs in transit-station lakes for water diversion are not well documented or understood. In this study, a comprehensive investigation of QNs in water, sediment, and aquatic fauna, including norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENR), and ofloxacin (OFL), was conducted in Luoma Lake, a major transit station for the eastern route of the South-to-North Water Diversion Project in China. The target QNs were widely distributed in the water (∑QNs: 70.12 ± 62.79 ng/L) and sediment samples (∑QNs: 13.35 ± 10.78 ng/g dw) in both the non-diversion period (NDP) and the diversion period (DP), where NOR and ENR were predominant. All the QNs were detected in all biotic samples in DP (∑QNs: 80.04 ± 20.59 ng/g dw). The concentration of ∑QNs in the water in NDP was significantly higher than those in DP, whereas the concentration in the sediments in NDP was comparable to those in DP. ∑QNs in the water-sediment system exhibited decreasing trends from northwest (NW) to southeast (SE) in both periods; however, the K_oc (organic carbon normalized partition coefficients) of individual QNs in DP sharply rose compared with those in NDP, which indicated that water diversion would alter the environmental fate of QNs in Luoma Lake. In DP, all QNs, excluding NOR, were all biodiluted across the food web; whereas their bioaccumulation potentials in the SE subregion were higher than those in the NW subregion, which was in contrast to the spatial distribution of their exposure concentrations. The estimated daily QN intakes via drinking water and aquatic products suggested that residents in the SE side were exposed to greater health risks, despite less aquatic pollution in the region.

Sulfamethoxazole removal from mariculture wastewater in moving bed biofilm reactor and insight into the changes of antibiotic and resistance genes

Antibiotics are widely dosed in mariculture sector, resulting in substantial antibiotics residues. Hence, mariculture wastewater is urgent to be treated before discharging. In this study, the anoxic/oxic moving bed biofilm reactor (A/O-MBBR) was used to treat the wastewater containing sulfamethoxazole (SMX) from mariculture, SMX removal mechanism and the variation of antibiotic-resistant genes (ARGs) were investigated. The results showed that 22%-33% of SMX was removed by the bioreactor, where a small amount of SMX was adsorbed and stored by the extracellular polymers and most of SMX (>80%) was biodegraded in the anoxic tank. Occurrence of nitrate in anoxic condition was conducive to SMX degradation. Pseudomonas, Desulfuromusa, and Methanolobus species, as well as microbial catalase contributed to the SMX biotransformation. Quantitative PCR analysis of ARGs (sul1, sul2 and int1) and mRNA (sul1, sul2) showed that SMX enriched SMX-related ARGs and enhanced the expression of corresponding genes. Most of ARGs finally were discharged with effluent. Hence, the effluent from biologically based processes treating mariculture wastewater still contained antibiotics residue and resistance genes, which should be further controlled by suitable techniques.

Historical exposure to chemicals reduces tolerance to novel chemical stress in Daphnia (waterflea)

Until the last few decades, anthropogenic chemicals used in most production processes have not been comprehensively assessed for their risk and impact on wildlife and humans. They are transported globally and usually end up in the environment as unintentional pollutants, causing long‐term adverse effects. Modern toxicology practices typically use acute toxicity tests of unrealistic concentrations of chemicals to determine their safe use, missing pathological effects arising from long‐term exposures to environmentally relevant concentrations. Here, we study the transgenerational effect of environmentally relevant concentrations of five chemicals on the priority list of international regulatory frameworks on the keystone species Daphnia magna. We expose Daphnia genotypes resurrected from the sedimentary archive of a lake with a known history of chemical pollution to the five chemicals to understand how historical exposure to chemicals influences adaptive responses to novel chemical stress. We measure within‐ and transgenerational plasticity in fitness‐linked life history traits following exposure of “experienced” and “naive” genotypes to novel chemical stress. As the revived Daphnia originate from the same genetic pool sampled at different times in the past, we are able to quantify the long‐term evolutionary impact of chemical pollution by studying genome‐wide diversity and identifying functional pathways affected by historical chemical stress. Our results suggest that historical exposure to chemical stress causes reduced genome‐wide diversity, leading to lower cross‐generational tolerance to novel chemical stress. Lower tolerance is underpinned by reduced gene diversity at detoxification, catabolism and endocrine genes in experienced genotypes. We show that these genes sit within pathways that are conserved and potential chemical targets in other species, including humans.

A recent advancement on nanomaterials for electrochemical sensing of sulfamethaoxole and its futuristic approach

Sulfamethoxazole (SMX) forms the high harmfulness and causing negative health impacts to well-being human and environment that found to be major drastic concern. It is subsequently important to keep in track for monitoring of SMX through convenient detecting devices which include the requirement of being minimal expense and potential for on location environmental applications. Nanomaterials based design has been proposed to determine the SMX antibiotic which in turn provides the solution for this issue. In spite of the critical advancement accomplished in research, further endeavors are yet to foster the progress on electrochemical sensors with the guide of various functional nanomaterials and guarantee the effective transportability for such sensors with improved coherence. Moreover, it has been noticed that, only few reports on electrochemical sensing of SMX detection using nanomaterials was observed. Hence an in-depth evaluation of electrochemical sensing systems using various nanomaterials for SMX detection was summarized in this review. Additionally this current review centers with brief presentation around SMX hazard evaluation followed by study on the current logical techniques to feature the importance for SMX detection. This review will provide the sum up view towards the future ideas of this field which assists in improving the detecting strategies for SMX detection.

How anammox process resists the multi-antibiotic stress: Resistance gene accumulation and microbial community evolution

The effects of multiple antibiotics on the anaerobic ammonia oxidation (anammox) process were investigated. The resistance of the anammox system to high-concentration antibiotics was also demonstrated through gradual acclimation experiments. Inhibition of the anammox process (R₁) occurred when the concentrations of erythromycin (ERY), sulfamethoxazole (SMX) and tetracycline (TC) were 0.1, 5.0 and 0.1 mg L^-1, respectively. The nitrogen removal efficiency (NRE) of R₁ was reduced from 97.2% to 60.7% within 12 days and then recovered to 88.9 ± 9.5% when the nitrogen loading declined from 4.52 ± 0.69 to 2.11 ± 0.58 kg N m^-3 d^-1. Even when the concentrations of ERY, SMX and TC were as high as 1.0, 15.0 and 1.0 mg L^-1, respectively, R₁ maintained stable operation. The increases in the abundance of antibiotic resistance genes (ARGs) and in extracellular polymeric substances (EPS) content showed that the anammox process alleviated stress from multiple antibiotics mainly by producing ARGs and secreting EPS. The molecular docking simulation results illustrated the potential binding sites between ammonium transporter and different antibiotics. The upregulation of functional gene expression and the stable abundance of Candidatus Kuenenia in R₁ compared with that in the control suggested that the R₁ reactor generally maintained more stable long-term operation. This work provides a new understanding of the application of the anammox process to treat wastewater containing multiple antibiotics.

Sediments alleviate the inhibition effects of antibiotics on denitrification: Functional gene, microbial community, and antibiotic resistance gene analysis

Both antibiotics and sediments can affect the denitrification in aquatic systems. However, little is known how antibiotics influence the denitrification in the presence of sediments. Here, the effects of antibiotics (sulfamethoxazole, tetracycline and ofloxacin) on denitrification in the absence and presence of sediments were investigated. The influencing mechanisms were revealed by quantifying the denitrification functional genes (DNGs), 16S-seq of bacteria, and antibiotic resistance genes (ARGs). The results showed that the presence of antibiotics inhibited NO₃-N reduction by decreasing the abundances of narG, nirK, nosZ, total DNGs, and denitrifying bacteria. However, the inhibition effect was alleviated by sediments, which promoted the growth of bacteria and decreased the selective pressure of antibiotics as the vector of bacteria and antibiotics, thus increasing the abundances of denitrifying bacteria and all the DNGs. Partial least-squares path model disclosed that antibiotics had negative effects on bacteria, ARGs and DNGs, while sediments had negative effects on ARGs but positive effects on bacteria and DNGs. The network analysis further revealed the close relation of the genera Bacillus, Acinetobacter, and Enterobacter with the ARGs and DNGs. The findings are helpful to understand the denitrification in antibiotic-polluted natural waters.

Typology of interventions for antimicrobial use and antimicrobial resistance in aquaculture systems in low- and middle-income countries

Indiscriminate antimicrobial use (AMU) in aquaculture to treat and prevent diseases is common and can lead to the emergence of antimicrobial-resistant micro-organisms, potentially impacting public health and connected ecosystems. This study aimed to develop a typology to classify and characterise interventions to reduce AMU in aquaculture and identify points of action. Seventeen aquaculture and animal health professionals in Asian and African countries were interviewed to gather information on characteristics of interventions in different contexts to develop a typology. Seven types of interventions were defined: (i) legislation and regulations; (ii) industry rules and standards; (iii) voluntary instruments; (iv) commercial technology and alternatives to antimicrobials; (v) on-farm management; (vi) learning and awareness-raising; and (vii) activities with co-benefits. Types were based on intervention function, scope of implementation, implementer, compulsion, strength of the intervention, AMU/antimicrobial resistance (AMR) objective and stakeholder to influence. For each type, examples were described and discussed. The most common interventions to address AMU and AMR were legislative and regulatory frameworks and voluntary instruments, including National Action Plans. Interventions addressing AMU/AMR specifically were scarce. Other interventions focused on indirect effect pathways to AMU and AMR reduction aiming to improve good aquaculture practices, disease prevention and improved management. Monitoring and evaluation of these interventions were found to be rare, only present for interventions driven by development projects and international agencies. The presented typology of existing strategies and interventions addressing AMU/AMR in aquaculture systems can guide evaluation of AMR-sensitive interventions that promote responsible AMU, and informs the design and implementation of future interventions.

Source-specific risk apportionment and critical risk source identification of antibiotic resistance in Fenhe River basin, China

A comprehensive understanding of the sources and distribution of antibiotic resistance risk is essential for controlling antibiotic pollution and resistance. Based on surface water samples collected from the Fenhe River basin in the flood season, using the positive matrix factorization (PMF) model, the risk quotient (RQ) method and the multiple attribute decision making (MADM) method, the resistance risk and source-specific resistance risk of antibiotics were analyzed in this study. The results showed that sulfonamides (SAs) were the dominant antibiotics with a mean concentration of 118.30 ng/L, whereas tetracyclines (TCs) and macrolides (MLs) had the highest detection frequencies (100%). The significant resistance risk rate of antibiotics in the entire river basin was 48%, but no high risk occurred. The significant resistance risk rate of quinolones (QNs) was the highest (100%), followed by that of MLs and TCs. Owing to human activities, the most serious resistance risk occurred in the midstream of the river basin. The resistance risk was the lowest upstream. The antibiotics were mainly contributed by six sources. Pharmaceutical wastewater was the main source, accounting for 30%, followed by livestock discharge (22%). The resistance risk from the six sources showed clear differences, but none of the sources caused a high risk of antibiotic resistance. Pharmaceutical wastewater poses the greatest risk of antibiotic resistance in the Fenhe River basin and is widely distributed. The second greatest source was livestock discharge, which was mainly concentrated in the upstream and midstream areas. The critical sources upstream, midstream, and downstream were all pharmaceutical wastewater, whereas the sequences of other sources were different because different areas were affected by different human activities. The proposed method might provide an important reference for the identification the key source of antibiotics and management of antibiotic pollution, as well as help for the management of antibiotics in Fenhe and Shanxi Province.

Contribution of enrofloxacin and Cu2+ to the antibiotic resistance of bacterial community in a river biofilm

Pollutants discharged from wastewater are the main cause of the spread of antibiotic resistance in river biofilms. There is controversy regarding the primary contribution of environmental selectors such as antibiotics and heavy metals to the development of antibiotic resistance in bacterial communities. Here, this study compared the effect of environmental safety concentration Cu²⁺ and enrofloxacin (ENR) on the evolution of antibiotic resistance by examining phenotypic characteristics and genotypic profiles of bacterial communities in a river biofilm, and then distinguished the major determinants from a comprehensive perspective. The pollution induced community tolerance in ENR-treated group was significantly higher than that in Cu²⁺-treated group (at concentration levels of 100 and 1000 μg/L). Metagenomic sequencing results showed that ENR significantly increased the number and total abundance of antibiotic resistance genes (ARGs), but there was no significant change in the Cu²⁺- treated group. Compared with Cu²⁺, ENR was the major selective agent in driving the change of taxonomic composition because the taxonomic composition in ENR was the most different from the original biofilm. Comparing and analyzing the prokaryotic composition, the phylum of Proteobacteria was enriched in both ENR and Cu²⁺ treated groups. Among them, Acidovorax and Bosea showed resistance to both pollutants. Linking taxonomic composition to ARGs revealed that the main potential hosts of fluoroquinolone resistance genes were Comamonas, Sphingopyxis, Bradyrhizobium, Afipia, Rhodopseudomonas, Luteimonas and Hoeflea. The co-occurrence of ARGs and metal resistance genes (MRGs) showed that the multidrug efflux pump was the key mechanism connecting MRGs and ARGs. Network analysis also revealed that the reason of Cu²⁺ selected for fluoroquinolones resistant bacterial communities was the coexistence of multidrug efflux gene and MRGs. Our research emphasizes the importance of antibiotics in promoting the development of antibiotic resistant bacterial communities from the perspective of changes in community structure and resistome in river biofilms.

Delayed toxicity of three fluoroquinolones and their mixtures after neonatal or embryonic exposure, in Daphnia magna

Fluoroquinolones (FQs) are antibacterial drugs, used both in human and veterinary medicine, that are currently considered as emerging micropollutants. This study investigated the delayed toxic effects of enrofloxacin (ENR), flumequine (FLU), levofloxacin (LEV) and their binary mixtures in D. magna. For this purpose, a 10-day follow-up in pure medium was added to the standard D. magna immobilization test. During this follow-up, phenotypic alterations were evidenced, which were related to scarce or zeroed egg production and early mortality. Consequently, the EC_50 s recalculated at the end of the follow-up were always remarkably lower than those obtained after the 48 h immobilization test: ENR 3.13 vs. 16.72 mg L^-1; FLU 7.18 vs. 25.35 mg L^-1; LEV 15.11 vs. > 40 mg L^-1. To analyse the possible interactions within the binary mixtures, the method of nonlinear additive isoboles was applied. The three compounds showed invariably to follow the principle of concentration addition. Furthermore, as previous experiments showed toxicity of FLU and ENR after embryonic exposure of D. magna at a concentration of 2 mg L^-1, an additional two embryonic tests were conducted with identical design: one with 2 mg L^-1 LEV and the other with a ternary mixture containing 0.66 mg L^-1 of each of the three FQs. The embryos were exposed for three days in vitro to the drug solutions and were then reconducted to pure medium for 21 days observation. Both the tests ended-up with only non-significant effects on growth and reproduction, confirming the lower toxicity of LEV, when compared to ENR and FLU, and the absence of any evident synergistic interaction among the three FQs. Overall, these studies have shown two relevant features related to the toxicity of the three FQs: (1) they give rise to delayed toxic effects in D. magna that are undetectable by the standard immobilization test; (2) their interaction in mixtures follow the principle of Concentration Addition. Both these indications concern the Environmental Risk Assessment of FQs and may be of interest to regulatory authorities.

Toxicity of fluoroquinolones on the cladoceran Daphnia magna

This study evaluates the acute and chronic toxicological effects of six fluoroquinolones on the mortality and growth of Daphnia magna. The NOECs calculated with the multivariate Probit regression model for the chronic study were 56 μg/L ciprofloxacin, 63 μg/L enrofloxacin, 78 μg/L levofloxacin, 85 μg/L marbofloxacin, 69 μg/L norfloxacin, and 141 μg/L ofloxacin. The risk quotients were determined using the measure environmental concentrations reported in water sources from different countries. The risks were low and moderate in water samples from rivers and lakes, although concentrations of ciprofloxacin, norfloxacin, and ofloxacin reported in some countries can cause toxicological damage to D. magna. In addition, urban wastewater and hospital wastewater samples constitute a threat to D. magna (high and moderate risks), requiring the treatment of these wastewater. PRACTITIONER POINTS: The NOECs calculated with the multivariate Probit model for the six fluoroquinolonas are between 56 μg/L ciprofloxacin and 141 μg/L ofloxacin. The levels of ciprofloxacin, norfloxacin, and ofloxacin in urban wastewater and hospital wastewater produce moderate and high risks for D. magna. Water and river samples from some countries containing ciprofloxacin, norlfoxacin, and ofloxacin present high risks for D. magna.

Biochar-Supported TiO2-Based Nanocomposites for the Photocatalytic Degradation of Sulfamethoxazole in Water-A Review

Sulfamethoxazole (SMX) is a frequently used antibiotic for the treatment of urinary tract, respiratory, and intestinal infections and as a supplement in livestock or fishery farming to boost production. The release of SMX into the environment can lead to the development of antibiotic resistance among the microbial community, which can lead to frequent clinical infections. SMX removal from water is usually done through advanced treatment processes, such as adsorption, photocatalytic oxidation, and biodegradation. Among them, the advanced oxidation process using TiO2 and its composites is being widely used. TiO2 is a widely used photocatalyst; however, it has certain limitations, such as low visible light response and quick recombination of e-/h+ pairs. Integrating the biochar with TiO2 nanoparticles can overcome such limitations. The biochar-supported TiO2 composites showed a significant increase in the photocatalytic activities in the UV-visible range, which resulted in a substantial increase in the degradation of SMX in water. The present review has critically reviewed the methods of biochar TiO2 composite synthesis, the effect of biochar integration with the TiO2 on its physicochemical properties, and the chemical pathways through which the biochar/TiO2 composite degrades the SMX in water or aqueous solution. The degradation of SMX using photocatalysis can be considered a useful model, and the research studies presented in this review will allow extending this area of research on other types of similar pharmaceuticals or pollutants in general in the future.

Increasing disease burden and use of drugs and chemicals in Bangladesh shrimp aquaculture: A potential menace to human health

Using structured surveys in 2008 and 2016, change in disease burden and use of chemical treatments in Bangladesh shrimp farm management was examined. Overall, disease burden had increased in all farms and was more polarized, with a fewer number of individual infectious diseases responsible for most disease in ponds. Farmers also reported physical deformities, nutritional deficiencies, and unknown diseases further indicating poor health of their stock. To combat the threat, more chemical treatments were used (5.2 treatments per farm in 2008 versus 28.8 in 2016), resulting in an average increase of 424% in the number of active substances entering shrimp ponds. Although there was a modest reduction in the use of antimicrobials, shrimp was being exposed to a wider range of chemicals during rearing. The subsequent concern for the environment, animal and human health demands further research to identify potential risks from residues of chemical products.

Toxicity and combined effects of antibiotics and nano ZnO on a phosphorus-removing Shewanella strain in wastewater treatment

Antibiotics and nanoparticles, which are emerging contaminants, can occur simultaneously in biological wastewater treatment systems, potentially resulting in complex interactive effects. This study investigated the effects of individual and complex zinc oxide nanoparticles (nZnO) and antibiotics (quinolone and sulfonamide), on the Shewanella strain used to remove phosphorus (PO₄^3-), metabolic processes, as well as its complexing and toxicity mechanisms. The inhibition of PO₄^3- removal increased from 30.7% to 100.0% with increased nZnO concentrations (half maximal effective concentration (EC50) = 1.1 mg Zn/L) by affecting poly-p and glycogen metabolites. The combined exposure to nZnO and ciprofloxacin/norfloxacin (CIP/NOR) had a significant antagonistic effect on the removal of PO₄^3- and on the metabolism of poly-p and glycogen in phosphate-accumulating organisms (PAOs), whereas the complexing of sulfonamide and nZnO had no significant additional effect. Thus, the complexing of nanoparticles and antibiotics exhibited different toxicity effects from the antibiotic structure-based complex reactions. These results can be used to improve wastewater treatment processes and reduce risks associated with wastewater discharge.

Emerging contaminants detected in aquaculture sites in Java, Indonesia

Pharmaceuticals of emerging concern (acetaminophen (ACM), trimethoprim (TMP), oxytetracycline (OTC), and sulfamethoxazole (SMX)) were detected in water samples from aquaculture environments and nonaquaculture sites in four regions located on the northern coast of Central Java. ACM was the most prevalent pharmaceutical, with a mean concentration ranging from not detected (n.d.) to 5.5 ± 1.9 ngL^-1 (Brebes). Among the target antibiotics (TMP, OTC, SMX), OTC was the most ubiquitous, with a mean concentration varying from n.d. to 8.0 ± 3.3 ngL^-1. Correlation analysis demonstrated that there was a significant correlation between TMP and SMX concentrations. Based on ecological risk assessment evaluation, the use of OTC requires serious consideration, as it presented high health risks to algae, while ACM, TMP, and SMX posed an insignificant to moderate risk to algae, invertebrates, and fish. The findings obtained from this study highlight OTC as an emerging contaminant of prominent concern. More attention needs to be given to managing and planning for the sustainable management of shrimp farms, particularly in the northern part of Central Java.

Prevalence, Virulence Gene Distribution and Alarming the Multidrug Resistance of Aeromonas hydrophila Associated with Disease Outbreaks in Freshwater Aquaculture

The study aims to evaluate the infection prevalence, virulence gene distribution and antimicrobial resistance of Aeromonas hydrophila associated in diseased outbreaks of cultured freshwater fish in Northern Vietnam. The confirmed A. hydrophila were screened for the presence of the five pitutative-virulence genes including aerolysin (aerA), hemolysin (hlyA), cytotonic enterotoxin (act), heat-labile cytotonic enterotoxin (alt), and heat-stable enterotoxin (ast), and examined the susceptibility to 16 antibiotics. A total of 236 A. hydrophila isolates were recovered and confirmed from 506 diseased fish by phenotypic tests, PCR assays, and gyrB, rpoB sequenced analyses, corresponding to the infection prevalence at 46.4%. A total of 88.9% of A. hydrophila isolates harbored at least one of the tested virulence genes. The genes aerA and act were most frequently found (80.5% and 80.1%, respectively) while the ast gene was absent in all isolates. The resistance to oxacillin, amoxicillin and vancomycin exhibited the highest frequencies (>70%), followed by erythromycin, oxytetracycline, florfenicol, and sulfamethoxazole/trimethoprim (9.3–47.2%). The multiple antibiotic resistance (MAR) index ranged between 0.13–0.88 with 74.7% of the isolates having MAR values higher than 0.2. The results present a warning for aquaculture farmers and managers in preventing the spread of A. hydrophila and minimizing antibiotic resistance of this pathogen in fish farming systems.